ConclusionThe rheological behaviour of two white pigments based paintshas been investigated, according to reconstructions of 19th centuryartistic formulations. As particulate pastes, their macroscopic rhe-ology is dominated by the existence of a fluid-to-solid transition. Atstresses above the so-called yield stress, the materials flow like vis-cous liquids, whereas they behave like solids at lower stresses withproperties that evolve slowly with time. We could underline theeffect of paint formulation (pigment content and nature but alsooil treatment) on the rheological properties of zinc and lead white.The differences between both pigments are related to their chem-ical composition inducing different interactions with oil, as wellas to their specific size and shape of grains. The lead white grainsare indeed particularly anisotropic (“needle”-shaped for cerussitegrains or hexagonal flat grains in the case of hydrocerussite), con-trary to the more isotropic grains of zinc white.The main difficulty of these experiments lay in the nature ofthe samples: they exhibit a complex behaviour with possible timedependent effects. Moreover the data interpretation is also compli-cated. It is not possible to predict behaviour of paint formulationsafter application with precision: only an estimation of their level-ling properties can be provided. This question remains a big issue inthe paint industry as many other parameters than the yield stressvalue would have to be considered especially in the case of timedependent